Terms of Service

Key Terms at a Glance

Here's a quick summary of the most important points in our Terms of Service:

Term	What It Means
Educational use only	Our calculator is an informational tool, not a medical device. Results are estimates only.
Not birth control	Do not rely on this calculator to prevent pregnancy. The calendar method has a 12-24% typical failure rate for contraception.
Not medical advice	We provide educational content, not medical diagnoses or treatment recommendations. Consult a healthcare provider for medical concerns.
Free to link	You may link to our site from blogs, social media, or websites without permission. Embedding requires prior approval.
Privacy-focused	All calculations happen in your browser. We don't store your health data. See our Privacy Policy for details.

Acceptance of Terms

By accessing and using the Ovulation Calculator website ("the Site"), you acknowledge that you have read, understood, and agree to be bound by these Terms of Service ("Terms"). If you do not agree to these Terms, please do not use the Site.

These Terms apply to all visitors, users, and others who access or use the Site. Your continued use of the Site following any changes to these Terms constitutes acceptance of those changes.

Description of Service

Ovulation Calculator provides free online calculator tools designed to help users estimate ovulation dates, fertile windows, and related fertility information based on menstrual cycle data. The service includes:

An ovulation date calculator
Fertile window estimation
Next period prediction
Due date estimation (if conception occurs)
A 3-month fertility calendar
Educational articles about fertility and menstrual cycles

No account registration is required to use the calculator. The service is accessible via standard web browsers on desktop and mobile devices. All calculations are performed locally in your browser.

Understanding Medical Disclaimers

It is important to understand the distinction between different categories of health-related tools. Our calculator is an informational tool, not a medical device. The table below clarifies these categories:

Category	Examples	Regulatory Oversight	Our Calculator
FDA-Cleared Medical Device	Natural Cycles app (FDA-cleared for contraception), Clearblue Fertility Monitor	Regulated by FDA; must demonstrate safety and efficacy through clinical trials	No -- we are not FDA-cleared and do not claim to be
Digital Health Tool	Flo, Clue, Ovia (period tracking apps with health features)	Generally not FDA-regulated; may be subject to FTC enforcement for false claims	No -- we don't track health data over time or create health profiles
Informational/Educational Tool	Online calculators, educational websites, reference charts	Not regulated as medical devices; must not make diagnostic or therapeutic claims	Yes -- this is our category. We provide estimates for educational purposes only
Clinical Diagnostic Tool	Transvaginal ultrasound, hormone blood tests, HSG	Performed by licensed healthcare providers; results used for medical decisions	No -- our calculator cannot diagnose any condition

Key takeaway: Our calculator provides estimates based on the calendar method for educational purposes. For medical decisions about fertility, contraception, or reproductive health, always consult a qualified healthcare provider. See ACOG or WHO for evidence-based guidance.

Disclaimer of Warranties

The calculations and information provided by this Site are for informational and educational purposes only. The Site is provided "as is" and "as available" without any warranties of any kind, either express or implied.

Specifically, this calculator:

Is NOT medical advice. The information provided does not constitute medical, health, or professional advice of any kind.
Is NOT a diagnostic tool. The calculator cannot diagnose fertility issues, medical conditions, or pregnancy.
Is NOT a contraceptive method. The calendar method alone has a typical failure rate of 12-24% for pregnancy prevention. Do not rely on this calculator as a method of birth control.
Does NOT guarantee outcomes. Using this calculator does not guarantee pregnancy, conception, or any specific fertility outcome.

Results should be considered estimates only. For medical decisions, fertility concerns, or reproductive health questions, always consult a qualified healthcare provider, gynecologist, or reproductive specialist.

Contraception Effectiveness Comparison

To underscore why our calculator should not be used for birth control, here are failure rates for various contraceptive methods, comparing perfect use with typical use:

Contraceptive Method	Perfect-Use Failure Rate	Typical-Use Failure Rate	Notes
Calendar/Rhythm Method	5%	12-24%	What this calculator uses; unreliable for contraception
Fertility Awareness (Symptothermal)	0.4%	2-23%	Combines BBT, cervical mucus, and calendar; requires training
Male Condom	2%	13%	Also protects against STIs
Combined Oral Contraceptive (Pill)	0.3%	7%	Requires daily adherence; prescription needed
Hormonal IUD	0.2%	0.2%	Highly effective; lasts 3-7 years depending on type
Copper IUD	0.6%	0.8%	Non-hormonal; lasts up to 10 years
Implant (Nexplanon)	0.05%	0.05%	Most effective reversible method; lasts 3 years

Data source: CDC: Contraception. Failure rates represent the percentage of women experiencing an unintended pregnancy within the first year of use.

Typical-Use Failure Rates Visualized

This chart illustrates why the calendar method alone should not be relied upon for contraception:

Calendar/Rhythm Method

24%

Male Condom

13%

Oral Contraceptive (Pill)

7%

Symptothermal Method

2%

Copper IUD

<1%

Hormonal IUD

<1%

Implant (Nexplanon)

<1%

Chart shows typical-use failure rate (% of women experiencing unintended pregnancy in first year).

For evidence-based contraception guidance, consult your healthcare provider or visit: ACOG: Contraception Information | WHO: Family Planning Fact Sheet | Planned Parenthood: Birth Control

Limitation of Liability

To the fullest extent permitted by applicable law, we shall not be liable for any direct, indirect, incidental, special, consequential, or punitive damages arising from or related to your use of, or inability to use, the Site or its content.

This includes, but is not limited to:

Any decisions, actions, or outcomes based on calculator results
Unintended pregnancy or failure to conceive
Any health-related consequences
Errors or inaccuracies in calculations
Service interruptions or unavailability

You use this Site and its calculator tools entirely at your own risk. You are solely responsible for any decisions you make based on the information provided.

Accuracy

We strive for accuracy in our calculations based on established biological principles and widely-accepted formulas. The calculator uses the calendar method, which assumes a 14-day luteal phase (the time between ovulation and your next period).

However, we do not guarantee the accuracy of results because:

Individual menstrual cycles vary significantly
Ovulation timing can be affected by stress, illness, travel, and other factors
The 14-day luteal phase is an average; individual luteal phases range from 10-16 days
Irregular cycles make calendar-based predictions less reliable

The formulas and methodology used by the calculator are documented on our About page. For improved accuracy, consider combining calendar predictions with ovulation predictor kits, basal body temperature tracking, or other fertility awareness methods.

Permitted Use

You may use the Site for personal, non-commercial purposes in accordance with these Terms. Specifically:

Personal use: You may use the calculator for your own personal fertility tracking and education.
Linking: You may link to our Site from your own website, blog, or social media without prior permission.

You may NOT:

Scrape or crawl: Use automated tools, bots, or scripts to access, scrape, or collect data from the Site.
Embed without permission: Embed our calculator in your website using iframes or similar methods without prior written permission.
Copy content: Reproduce, distribute, or republish substantial portions of our content, articles, or code without permission.
Commercial use: Use our content or tools for commercial purposes without authorization.
Misrepresent: Imply affiliation with or endorsement by us without permission.

If you wish to embed our calculator or use our content in ways not covered above, please contact us to discuss.

Intellectual Property

The Site's design, layout, graphics, text content, code, and other materials are protected by copyright and other intellectual property laws. You may not reproduce, modify, distribute, or create derivative works without our prior written consent.

The underlying mathematical formulas used for calculations (such as subtracting 14 days from cycle length to estimate ovulation) are part of the public domain and are not claimed as proprietary. However, our specific implementation, presentation, and accompanying content are protected.

External Links

The Site may contain links to third-party websites, resources, or services. These links are provided for convenience and informational purposes only. We do not control, endorse, or assume responsibility for the content, privacy policies, or practices of any third-party sites.

Accessing external links is at your own risk. We encourage you to review the terms and privacy policies of any third-party sites you visit.

Modifications to Terms

We reserve the right to modify these Terms at any time. When we make changes, we will update the "Last Updated" date at the top of this page. We may also notify users of significant changes through a notice on the Site.

Your continued use of the Site after any modifications to the Terms constitutes your acceptance of the revised Terms. If you do not agree to the modified Terms, you should discontinue use of the Site.

Termination

We reserve the right to restrict, suspend, or terminate access to the Site, in whole or in part, at any time and for any reason, including but not limited to violations of these Terms. We may do so without prior notice or liability.

Your Rights as a User

We believe in transparency and respect for our users. Here are the key rights you have when using our website:

Privacy by Design

Your health data is never collected, stored, or transmitted. All calculations run locally in your browser. You have full control over your information at all times.

Transparent Information

We clearly explain our methodology, limitations, and how our calculator works. No hidden fees, no surprise data collection, no misleading health claims.

Free and Open Access

No registration, login, or payment required. Full access to all calculator features and educational content without any barriers.

Non-Discrimination

Exercising your privacy rights (blocking cookies, using ad blockers, requesting data deletion) will never affect your access to our calculator or content.

Severability

If any provision of these Terms is found to be unenforceable or invalid by a court of competent jurisdiction, that provision shall be limited or eliminated to the minimum extent necessary, and the remaining provisions of these Terms shall remain in full force and effect.

Entire Agreement

These Terms, together with our Privacy Policy, constitute the entire agreement between you and us regarding your use of the Site and supersede any prior agreements or understandings. If you have questions about any of these terms, please contact us.

Contact

If you have questions about these Terms of Service, please contact us:

Email: info@calculateovulation.org

Related Pages

Privacy Policy — How we handle (and don't handle) your data
About Us — Our methodology, accuracy, and mission
Contact Us — Reach out with questions about these terms
Ovulation Calculator — Use our free fertility tracking tool

Calculator Accuracy Comparison

Different ovulation prediction methods vary widely in their accuracy. The table below compares the most common approaches so you can understand where a calendar-based calculator fits relative to clinical and at-home alternatives.

Prediction Method	Approximate Accuracy	How It Works	Limitations
Calendar Method	~80%	Estimates ovulation by subtracting 14 days from cycle length; this is the method used by our calculator	Assumes a regular cycle and a fixed 14-day luteal phase; less reliable for irregular cycles
Ovulation Predictor Kits (OPKs)	~97%	Detects the luteinizing hormone (LH) surge in urine that occurs 24-36 hours before ovulation	Can give false positives with PCOS or certain medications; requires daily testing near expected ovulation
Basal Body Temperature (BBT)	Retrospective confirmation	Tracks a small rise in resting body temperature (0.2-0.5 °F) that occurs after ovulation has already happened	Confirms ovulation only after the fact; cannot predict it in advance; disrupted by illness or poor sleep
Fertility Monitors	~99%	Tracks multiple hormones (estrogen and LH) to identify the full fertile window and pinpoint ovulation	Higher cost ($150-$300+); may not work well with very irregular cycles
Ultrasound (Follicular Tracking)	~100%	Directly visualizes follicle growth and ovulation via transvaginal ultrasound performed by a clinician	Requires multiple clinic visits; expensive; typically reserved for fertility treatment cycles

For the best results, many fertility specialists recommend combining the calendar method with at least one additional method, such as OPKs or BBT tracking. Learn more in our guide to ovulation predictor kits.

Understanding Calculator Limitations

There are several common misconceptions about what an online ovulation calculator can and cannot do. Understanding these will help you use the tool responsibly.

Myth: This calculator can be used as birth control.

Fact: The calendar method has a 12-24% typical-use failure rate for contraception. That means roughly 1 in 5 women relying solely on this method will experience an unintended pregnancy within a year. This calculator is designed to help identify fertile days for conception purposes, not to prevent pregnancy. For reliable birth control, consult your healthcare provider about evidence-based contraceptive options.

Myth: The calculator can diagnose fertility problems.

Fact: This is an educational tool, not a medical device. It cannot detect hormonal imbalances, blocked fallopian tubes, endometriosis, PCOS, or any other fertility condition. If you have been trying to conceive for 12 months (or 6 months if you are over 35) without success, consult a reproductive specialist. See our article on when to see a fertility specialist for guidance.

Myth: Calculator predictions are always accurate.

Fact: Accuracy varies significantly with cycle regularity. Women with consistent 26-32 day cycles will see more reliable predictions, while those with irregular cycles may find results less useful. Factors such as stress, illness, travel, weight changes, and hormonal fluctuations can all shift ovulation timing. For improved accuracy, consider supplementing calendar estimates with BBT tracking or cervical mucus monitoring.

Helpful External Resources

The following trusted organizations provide evidence-based information on reproductive health, fertility, and menstrual cycles.

ACOG — Women's Health The American College of Obstetricians and Gynecologists offers comprehensive resources on reproductive health, contraception, and fertility. Mayo Clinic — Getting Pregnant Mayo Clinic's fertility section covers ovulation tracking, timing intercourse, and understanding your menstrual cycle. RESOLVE — The National Infertility Association RESOLVE provides support, education, and advocacy for people affected by infertility, including guides to treatment options. NHS — Periods and Fertility The UK's National Health Service offers clear, medically reviewed information on periods, ovulation, and reproductive health.